Bean leaf beetle numbers have been increasing in Minnesota in recent years. This trend can be attributed to milder winters, which increase overwinter survival rates. Typically, the bean leaf beetle overwinters and as up to two generations. Overwintering beetles emerge early and feed on the unifoliate, but this feeding will rarely reach economic thresholds.
The first generation will normally emerge late spring into early summer, and primarily feed on young leafs. This generation should be treated if defoliation is greater than 35%, of the leaf surface. The second generation will emerge in late summer, typically during pod-set. Economic threshold for this generation is if defoliation exceeds 25%. The adults from the second generation will also feed on developing pods. Feeding on developing pods can hinder bean development, and allow disease to enter the plant. Economic threshold for pod-feeding beetles is when pod damage is greater than 10%. Scouting is the key to managing bean leaf beetle infestation.
Central Valley offers a number of methods to control bean leaf beetle infestation. Our agronomist will scout your bean fields periodically, in order to identify the first signs of the beetles. If bean leaf beetles are found within a given geography, adjacent fields will be closely watched. Also, if the infestation reaches threshold levels an insecticide can be used to control the insect. For more information or any questions you may have on bean leaf beetles, please contact your CVC Agronomist.
